Oscillatable driving tool for screw fasteners



United States Patent lnventor Victor A. Peckham, Jr.

1151 5th St., Manhattan Beach, California 90266 Appl. No. 742,941

Filed July 5, 1968 Patented Oct. 20, 1970 OSCILLATABLE DRIVING TOOL FOR SCREW FASTENERS 10 Claims, 1 1 Drawing Figs.

US. Cl .1 145/76, 192/41 Int. Cl B25b 15/04 F16d 13/08 Field of Search 145/76. 50. 70, 71, 66; 81/585, 58, 60; l92/41(S), 107. 107(M), 56(C), 81

[56] References Cited UNITED STATES PATENTS 2,810,463 10/1957 Williams 8 l /60UX 2,928,514 3/1960 Clausing et a1. 192/41 (S)UX 3,217,848 11/1965 Tout-Kowskyetal 192/41(S)UX Primary Examiner-Robert C. Riordon Assistant ExaminerRoscoe V. Parker, J r. Attorney-Brown, Critchlow, Flick and Peckham ABSTRACT: An elongated member has a hollow end portion provided with a pair of aligned openings adapted to receive a rotatable fastener-turning shaft A spring steel tape is wrapped upon itself between those openings to form a coil having an inner convolution adapted to frictionally engage the shaft. The outer end of the tape is anchored, and one side of the tape carries a layer of antifriction material between the convolutions of the coil. When the elongated member is oscillated around the shaft, the coil alternately grips and releases the shaft.

' Patented Oct. 20, 1970 Sheet 1 I v 1r ir:: 1 Z ,0. w J. K 47% V M P 1 M L. "I. T m a 2 W J r v y w a U W m N w 6 P h .U l ..ll .7 H -HII H. II 0 M M w OSCILLATABLE DRIVING TOOL FOR SCREW FASTENERS BACKGROUND OF THE INVENTION 3 There are three desirable features that every ratchet type wrench or screwdriver should have:

I. Adequate strength for handling the size nuts, bolts, and screws for which it is intended;

2. A small ratcheting" angle so that the tool is useable where space restricts the movement of its handle; and

3. Low reverse or return stroke torque. For instance, if a screw or bolt is being tightened in a nut or tapped hole, it is first run in with the fingers until increasing friction requires a wrench. If a ratchet wrench is used and its return stroke torque is too high, the screw will be turned clockwise and counterclockwise alternately as the wrench handle is swung back and forth, so no ratcheting action will take place and the screw will remain loose. Generally, the smaller the screw the lower the return stroke or free running torque must be in order to obtain ratcheting action.

When a wrench is to be used for driving %-inch and larger screws or bolts, the size of its head usually is not important, buta small head becomes very important when smaller size screws are to be driven because they often have very little clearance around them. The tool usually used in such cases is a screwdriver. If a ratchet wrench is to be used, it would be almost mandatory that the width of its head he not much greater than the screw head.

Most ratchet wrenches make use of teeth to obtain ratcheting, but some have attempted to use only a strip of spring steel that is coiled around the fastener or around a small driving shaft that turns the fastener. When the wrench handle is swung back and forth, the spring coil is supposed to alternately grip and release the fastener or driving shaft, but in practice the friction between the coil convolutions will not permit effective operation. This is because the coil convolutions must slip relative to one another as they alternately contract to grip and expand to release. If friction makes the convolution slippage difficult, then either the driving shaft will not be gripped at all or it will not be released on the reverse stroke. In either case, no ratcheting takes place.

One way of reducing the free running torque is simply to make the inside diameter of the coil larger, but there is a limit to the extent that the free running friction, called the residual friction, at the shaft can be reduced. This is because the residual friction between the inner turn of the coil and the shaft must be sufficient, when the coil is to turn the shaft, to cause the inner convolution to drag on the shaft enough to cause the next convolution to twist more tightly about the inner one. In order for a convolution to tighten and contract around the adjoining one, relative motion must occur between the two. If this relative motion between turns, which is very small, does not occur, the coil cannot tighten on the shaft. The tool will slip without driving.

I-Ieretofore, the residual friction between the inner turn of the coil and the shaft has had to be so great, due to the relatively high friction between the turns of the coil, that it increased the return stroke torque to the point where the coil often would not release the shaft at a reasonably low torsional level. It can be seen that the minimum amount of residual friction that is allowable between the coil and shaft depends largely upon the friction between the convolutions of the coil.

It is among the objects of this invention to provide an oscillating tool for driving fasteners, which can be made very small for small fasteners, which has a reliable driving action, which has an extremely low reverse stroke torque relative to its driving torque, which is strong and durable, which has a very small ratcheting angle, which can be used in confined areas, which is inexpensive, and which can be used for tightening or loosening threaded fasteners of different types and sizes.

The invention is illustrated in the accompanying drawings, in which:

FIG. I is a plan view;

FIG. 2 is a side view;

FIG. 3 is an enlarged fragmentary plan view with part of the top well broken away to show the coil;

FIG. 4 is an enlarged longitudinal section taken on the line IV-IV of FIG. I;

FIG. 5 is a further enlarged cross section taken on the line V-V of FIG. 3; FIGS. 6 and 7 are side views of two different fastener-turning shafts;

FIG. 8 is a plan view of a modified coil; 7

FIG, 9 is a cross section taken on the line IX-IX of FIG. 8;

FIG. 10 is a side view of still another driving shaft; and I FIG. 11 is an end view of the socket of FIG. 10.

Referring to FIGS. 1 to 5 of the drawings, the body of the tool or wrench is formed from an elongated member one that preferably is hollow throughout its length This member has opposite side walls two with curved ends. The portions of the side walls at one end are flat and parallel and of substantially uniform width for a short distance and then taper toward the opposite end. The hollow member can be formed from two identical half sections that engage each other along a joint three midway between the side walls. The wider end of the hollow member is the head of the tool and the rest of it serves as the handle.

Rigidly mounted in the hollow body of the tool near its head is a metal block 4, to one side of which one end of a spring metal tape Sis securely attached, such as by spot welding. The opposite edges of the tape are close to the two flat walls. The two half sections of the hollow member also can be spot welded to the block to hold the sections together. The tape extends forward from the block and is rolled into a coil having at least two convolutions, but preferably not more than four. The coil is concentric with a pair of axially aligned circular openings 6 and 7 in the flat side walls. These openings preferably are the same size so that a fastener-turning shaft can be inserted in them from either side of the body.

The driving shaft I0 has a cylindrical shank that fits snugly but rotatably in both openings so that there is no wobble of the shaft relative to the tool body. One projecting end of the shaft is shaped to mate with a fastener to turn it. Thus, the projecting end of the shank may be formed like the end of a screwdriver, for example. Between this end and the body of the tool the shaft is encircled by a shoulder 11 that bears against the outside of the body to take the axial loading or thrust on the shaft during use of the tool.

The inner convolution of the coil is wrapped around the shaft and frictionally engages it. The inner end may be bevelled to provide a better wrap. Before the shaft is inserted in the body, the inner diameter of the coil (the normal inside diameter of the inner convolution) is slightly less than the diameter of the shank. To facilitate insertion of the shaft in the coil, the end that is inserted may be tapered for a very short distance. Assuming that if the convolutions of the coil engage one another and the handle is swung in a clockwise direction in FIG. I, the coil will be contracted and tightened on the shaft and will turn it, but will not necessarily release the shaft when the handle is swung in the opposite direction because the friction between the turns of the coil may be greater than the friction between the fastener and the screw threads it engages.

It is a feature of this invention that the foregoing disadvantage of similar tools is overcome by constructing the tool in such a manner that the reverse stroke torque will be so low that in use the tool will make its return stroke without turning the fastener with it. This is accomplished by bonding a layer 14 of antifriction material in any suitable manner to one side of the metal tape between the coil convolutions, which it separates. That is, the antifriction layer bonded to one convolution also engages an adjoining convolution. The antifriction layer preferably is applied to the outer side of the tape, which is the side away from the shaft. If it were applied to the opposite side, friction between the first coil turn and the driving shaft would become unworkably low. This could be compensated for by making the inner turn of the coil smaller and thus tighter, but a normally small inner turn greatly increases the difficulty of inserting the shaft. Aside from that, the slippery layer inside the inner turn would soon be worn away by sliding around the shaft and by the insertion and removal of the shaft, and then the residual friction against the shaft would become undesirably high.

For best results, the antifriction material should have a low static coefficient of friction at low load levels. Materials with only a low dynamic coefficient of friction are not particularly useful, because virtually all relative movement of the convolutions takes place from the static condition. A material that has been found to possess the desired characteristics is polytetrafluorethylene, more commonly known as Teflon. Some nylons also may be suitable. The layer of antifriction material is as thin as possible in order not to increase the size of the coil any more than necessary.

Operation of the tool is as follows; A shaft is selected that has a projecting end which will fit the screw, bolt or nut to be tightened. Then the shaft is pressed into the coil, with portions of the shaft fitting in both openings in the tool body. The coil needs to engage the shaft only lightly, because the antifriction layer will allow the convolutions to slide on one another easily to tighten the coil on the shaft. After the driving end of the shaft has been engaged with the screw fastener, the handle of the wrench is swung back and forth around the fastener. As the handle moves in the forward or driving direction, the coil wraps itself tightly around the shaft and turns it. When the handle is moved in the opposite direction, the coil immediately unwraps itself slightly because the antifriction layer offers so little resistance to the turns sliding on one another. and friction between the coil and the shaft drops nearly to zero. The coil then is free to be rotated to its starting position without turning the shaft backwards with it. If it is desired to loosen a tight screw, the shaft is removed from the tool body and inserted again from the opposite side. The coil then will tighten when the handle is swung in the direction opposite to the driving direction, and the screw will be loosened.

As an example of a tool made in accordance with this invention, I have made one 2% inches long and five-sixteenth inch thick. The steel tape is one-quarter inch wide and .004 inch thick. The Teflon layer is the same width, but only .0005 inch thick. The head of the tool has only a ls-inch radius, which is important when working in tight spots, and the openings in it receive a shaft that is .187 inch in diameter. The inside diameter of the coil before the shaft is inserted is .l82 inch. lf that diameter were made smaller, it would become difficult to insert the shaft, while if the diameter were increased to .184, slippage often would occur during driving. Furthermore, as the inside diameter of the coil is increased, the tolerances for manufacturing a tool that works become so small that it is impractical to build it. The tool just described can be used in a very confined area. The head of the tool is so small it can be used where there is very little clearance around the screws. Although the driving torque amounts to 23 inch-pounds, the reverse stroke torque is so much less, due to the Teflon layer, that the coil readily releases itself from the shaft and does not attempt to reverse it. More torque could be handled if the radius of the head were larger, but this particular tool was designed for No. screws and smaller.

The thickness of the tape also is important from a manufacturing standpoint. If the tape is too thin, the torque capacity is reduced. if the tape is made too thick, the inner diameter of the coil becomes very critical and very difficult to maintain in production. A difference in diameter of only .002 inch can cover the range from doubled return stroke torque to unreliable drive stroke.

This tool has a very small ratcheting angle, which is governed by the elastic stretch of the materials in the tool and the small amount of compression in the Teflon coating. Both of these factors are, of course, load dependent. As a result, at maximum load of 23 inch-pounds the ratcheting angle is about 16". As the torque level drops, the angle decreases to a limiting value of about 5. This is due to coil unwrapping", which occurs as the torque goes through zero from the driving stroke value to the return stroke value, which is about inch-ounce.

in H0. 6 there is shown a fastener-driving shaft 16 having one end shaped to fit in'the socket of a'socket-head cap screw or the like. This modification also illustrates a way to prevent the wrench itself from being broken by applying too much force to it. Thus, by providing the shaft with a reduced diameter neck 17 of the right size between its thrust collar 18 and the driving end, the shaft will break at the neck before enough torque can be applied to the wrench to break the latter.

In some cases it may be desirable to be able to project the driving shaft different distances from the head of the wrench. As shown in H0. 7, this can be done by using a relatively long shaft 20 tightly encircled by a short plastic sleeve 21. The sleeve serves as a thrust member like the collars described be? fore, but the sleeve can be pushed along the shaft in either direction to leave any desired length of shaft projecting from the side of the wrench head at which the screw fastener is located.

As explained hereinbefore, a higher torque tool cannot be made by simply increasing the spring tape thicknesses, because the normal diameter of the inner convolution of the coil would become too critical. A way to solve the problem is shown in FIGS. 8 and 9, where another, but thinner, spring tape 23 extends along the outside of the main spring tape 24, with the layer of antifriction material 25 between them. The outer ends of the two tapes are fastened together or to the same anchoring member in the wrench. The two tapes are coiled together, but the thinner tape is shorter and terminates between the convolutions of the main coil.

The modified socket wrench shown in FIGS. 10 and 11 has a socket 27 provided with an open side to permit the socket to be slipped laterally over a nut or head of a cap screw where there is not enough clearance to allow the socket to be moved axially into place.

According to the provisions of the patent statutes, l have explained the principle of my invention and have illustrated and described what i now consider to represent its best embodiment. However. I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

lclaim:

l. A driving tool for screw fasteners, comprising an elongated member having a hollow end portion provided with a pair of parallel side walls, said walls having a pair of axially aligned openings therethrough adapted to receive a rotatable fastener-turning shaft, a spring steel tape wrapped upon itself between said walls to form a coil concentric with said openings, the inner convolution of the coil being adapted to encircle and frictionally engage the shaft, means anchoring the outer end of the tape, and a layer of antifriction material bonded to a side of said tape between the convolutions of the coil.

2. A driving tool according to claim 1, in which said antifriction layer is bonded to the outer side of the tape.

3. A driving too] according to claim I, in which said antifriction material is Teflon.

4. A driving tool according to claim 1, in which said member is hollow and said anchoring means is a block inside said member secured to the tape.

5. A driving too] according to claim 1, including a second spring steel tape extending along the antifriction side of the first-mentioned tape and coiled with it, means anchoring the outer end of the second tape, and means securing the inner end of the second tape to the first-mentioned tape.

6. A driving tool according to claim 1, including a shaft rotatably mounted in said openings and frictionally gripped by said tape for rotation thereby when the opposite end of said member is swung in the direction that tends to contract the coil, said shaft projecting outwardly from one of said side walls and having an outer end shaped to engage and turn a fastener.

7. A driving tool according to claim 6, in which said shaft is encircled between its outer end and said one wall by a thrust member engaged by the outer surface of that wall.

8. A driving tool according to claim 6, including a thrust sleeve frictionally mounted on said shaft between its outer end and said one wall and bearing against the outer surface of that wall.

9. A driving tool according to claim 6, in which said shaft is provided between its outer end and said coil with a weakened area adapted to break if the torque applied to the shaft by the 

